Crease-resistant security film

Abstract

The invention relates to a crease-resistant security film including: fibers; polyurethane aggregates, the proportion of said polyurethane amounting to between 5 and 45 wt. % in relation to the total dry weight of the fibers and the polyurethane, and said polyurethane having a break elongation that is higher than 600%; and a main cationic flocculant in a quantity of between 1 and 5 wt. % in relation to the total dry weight of the fibers and the polyurethane. The invention also relates to the method for the production of said film, and to a security document including said security film.

The invention claimed is: 
     
       1. A crease-resistant security sheet comprising:
 fibers, 
 polyurethane aggregates, the polyurethane being in a proportion of between 5% and 45% by dry weight relative to the total dry weight of the fibers and of the polyurethane and having an elongation at break of greater than 600%, and 
 a main cationic flocculating agent in an amount of between 1% and 5% by dry weight relative to the total dry weight of the fibers and of the polyurethane. 
 
     
     
       2. The security sheet as claimed in  claim 1 , wherein the proportion of said polyurethane is between 10% and 30% by dry weight relative to the total dry weight of the fibers and of the polyurethane. 
     
     
       3. The security sheet as claimed in  claim 1 , wherein said polyurethane has an elongation at break of greater than 1000%. 
     
     
       4. The security sheet as claimed in  claim 1 , wherein said polyurethane has a glass transition temperature below 0° C. 
     
     
       5. The security sheet as claimed in  claim 1 , wherein said polyurethane has a glass transition temperature below −25° C. 
     
     
       6. The security sheet as claimed in  claim 1 , wherein said polyurethane has a glass transition temperature below −40° C. 
     
     
       7. The security sheet as claimed in  claim 1 , wherein said polyurethane is selected from the group consisting of a polyurethane-polyester, a polyurethane-polyether, and a polyurethane-polycarbonate. 
     
     
       8. The security sheet as claimed in  claim 1 , wherein said polyurethane is a polyurethane-polyester. 
     
     
       9. The security sheet as claimed in  claim 1 , wherein said main cationic flocculating agent is selected from the group consisting of a cationic resin, polyacrylamides, polyethyleneimines, polyvinylamines, and mixtures thereof. 
     
     
       10. The security sheet as claimed in  claim 1 , wherein said main cationic flocculating agent is a polyamide-amine-epichlorohydrin resin. 
     
     
       11. The security sheet as claimed in  claim 1 , wherein said fibers comprise cellulosic fibers. 
     
     
       12. The security sheet as claimed in  claim 11 , wherein said cellulosic fibers is present in a proportion of greater than 60% by dry weight relative to the total dry weight of the fibers and of the polyurethane. 
     
     
       13. The security sheet as claimed in  claim 1 , wherein said fibers comprise synthetic fibers. 
     
     
       14. The security sheet as claimed in  claim 13 , wherein said synthetic fibers is present in an amount of between 5% and 30% relative to the total dry weight of the fibers and of the polyurethane. 
     
     
       15. The security sheet as claimed in  claim 1 , wherein said sheet comprises a secondary cationic flocculating agent selected from the group consisting of polyacrylamides, polyethyleneimine, polyvinylamines, and mixtures thereof, in an amount which may be between 0.1% and 0.5% by dry weight relative to the total dry weight of the fibers and of the polyurethane. 
     
     
       16. The security sheet as claimed in  claim 1 , wherein said sheet comprises at least one security element. 
     
     
       17. The security sheet as claimed in  claim 1 , wherein said sheet comprises an RFID device. 
     
     
       18. The security sheet as claimed in  claim 1 , wherein said sheet comprises an external surfacing layer. 
     
     
       19. A process for manufacturing a security sheet as described in  claim 1 , consisting in forming said sheet via a wet route from an aqueous suspension comprising:
 fibers, 
 an anionic dispersion of a polyurethane, and 
 a main cationic flocculating agent, 
 then draining and drying said sheet. 
 
     
     
       20. A process according to  claim 19 , wherein said polyurethane is in a proportion of between 5% and 45% by dry weight relative to the total dry weight of the fibers and of the polyurethane and has an elongation at break of greater than 600. 
     
     
       21. A process according to  claim 19 , wherein said main cationic flocculating agent is in an amount of between 1% and 5% by dry weight relative to the total dry weight of the fibers and of the polyurethane. 
     
     
       22. The process as claimed in  claim 19 , wherein said fibers, said anionic dispersion of polyurethane, and said main cationic flocculating agent are mixed in bulk. 
     
     
       23. A security document, comprising a security sheet as described in  claim 1 . 
     
     
       24. The security document as claimed in  claim 23 , wherein said document is a means of payment, an identity document, or a card. 
     
     
       25. The security document as claimed in  claim 24 , wherein said document is a banknote, a driving license, or a card.